1. Field of the Invention
The present invention relates to image formation processes and apparatus generally, and, more particularly, to an apparatus and process for adjusting a head gap in ink jet printers in dependence upon the thickness of printing paper in the ink jet printer.
2. Discussion of Related Art
In general, ink jet printers have a printer head that is mounted in a carriage. Cut sheets of paper to be printed with symbols by the printer head are drawn from a cassette seriatim and transferred under the influence of a pick-up roller to a position under the nozzle of the printer head. Conventional printers form images upon a medium such as a cut sheet of paper by propelling jets of ink from the nozzle in the bottom of the printer head and onto the paper positioned under the printer head. Typically, there a gap occurs between the printer head and the paper to be printed by the printer. I have found that when the paper is thicker than the general run of office paper stock (e.g., twenty pound xerographic paper), the paper all too frequency exhibits poor printing characteristics such as spread, stain with ink and inclination of the nozzle of the printer head, and resolution of the images being printed deviate due to variations between the gap between the paper being printed and the printer head. Conventional designs of printers such as those discussed in conjunction with FIGS. 1 and 2 below, either fail to provide for adjustment of this gap, or do not provide a convenient mechanism with which to readily and accurately adjust the gap.
In conventional and contemporary designs for ink jet printers, even if it is possible to adjust the head gap between the nozzle of the printer head and the printing paper so as to increase the gap along the front part of the carriage, because the nozzle is mounted with a inclination relative to the paper, if the number of holes in the nozzle is increased in order to increase the speed of printing, the nozzle becomes long. In recent designs, the length of the nozzle is about ten millimeters and differences in the height of the nozzle do occur. I have therefore, found that there is a problem in contemporary designs for ink jet printers, because of the occurrence of a deviations between the start point and the end point of the printing operation attributable to the feed roller. Efforts have been made in the art to adjust the head gap by rotating the carriage on the basis of deviations of the print operation. I have also found that these efforts cause additionally problems because the efficiency of the printing operation can be reduced by concomitant deviations in the resolution deviation when the print operation is performed on thicker printing stock such as on either an envelope or on a postcard.